The wireless access box is a wireless access terminal and is connected with the telephones through the interface provided by the subscriber interface circuit (such as the RJ11 interface), and it can use a variety of modes to implement wireless access services of different operators around the world, and achieve voice communications within the wireless network coverage.
In the existing router or the Ethernet switch, the transmission interfaces for the router or switch to interconnect and use can be implemented at the same time. In the interface of these existing equipments, generally the European standard E1 interface and the North American T1 interface are used, and these interfaces have different impedance types. Wherein, the E1 interfaces usually supports the peripherals with the impedances of 120 ohm and 75 ohm, and the T1 port supports the peripheral of 100 ohm. The telephones used by subscribers from different countries are different, and their internal impedances are also divided into three different types, thus the impedance matching of the wireless access box and the telephone becomes an issue.
At present, there is a solution for the three impedance standards of the E1 and T1 interfaces to change the parameter of the wireless access box interface circuit board and respectively select different impedance to match. Each interface mode corresponds to an interface circuit board respectively, thus a total of three interface circuit boards with different impedances should be designed in order to meet the demand for delivering the boards to a variety of regions. This solution has at least two disadvantages: an additional interface circuit board should be added, thus the design cost increases; there are such a great variety of interface circuit boards, thus the product configuration and management are not flexible enough.
Another solution is the manual configuration, that is, a DIP switch is designed in the motherboard of the wireless access box, and the DIP switch is dialed to select different impedance modes. This solution also has the following disadvantages:
(1) to achieve the matching of the three impedance modes, at least a 4-way DIP switch should be designed. Not only a position of the DIP switch should be designed in the appearance of the wireless access box, but also the cost of the DIP switch is high, extra PCB area of the motherboard of the wireless access box should be added, which doubly increases the cost;
(2) the actual operation is complicated, the subscriber's use needs additional instruction, otherwise, it is prone to manual errors;
(3) the metal reed contact is used within the DIP switch, and after a long time of many operations, the metal reed is likely to age, thus leading to poor contact and poor reliability.